Add -Ycook-comments to cook comments

[Duhemm]

This commit adds the -Ycook-comments option that will enable cooking
of the comments (type checking of @usecase in docstrings, expansion of
@define and @inheritdoc, etc.)

There are two reasons for introducing this configuration option:

• Cooking the comments slows the compilation down in cases where we
  are not interested in cooking them.
• Cooking the comments breaks -Ycheck, which prevents us from
  enabling -Ykeep-comments by default.